Process of preparing lubricating oil dye from cracked tar



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IVAPHTHA JOLUfiLE TAR DYE LIA/5 Patented Mar. 14, 1939 UNITED STATES PROCESS OF PREPARING LUBRICATING OIL DYE FROM CRACKED TAR Oliver H. Dawson, Baytown, Tex., assignor to Standard Oil Development Company, a corporation of Delaware Application December 1, 1934, Serial No. 755,569

7 Claims.

This invention relates to a process of preparing a dye for lubricating oils and will be fully understood from the following description when read in conjunction with the drawing, the sole figure of which is a diagrammatic representation, partly in section, of an apparatus appropriate for carrying out the invention.

Many lubricating oils, especially those prepared from asphaltic base stocks, have a bluish cast in reflected light. Such cast is not favored by the art and for that reason various processes have been proposed to improve the same and change it to a desirable green or greenish cast. My invention is concerned. with the preparation of dyes or coloring bodies which will impart a green fluorescence to lubricating oils when added in small quantities.

The raw material for my process is an extract obtained from a petroleum distillate by means of a selective solvent. There are a number of selective solvents known such as, for example, liquid sulfur dioxide, triphe-nyl phosphate, triortho-cresyl phosphate, aniline, furfural, etc., which dissolve constituents of an unsaturated and/r aromatic character from petroleum oils. The oil is agitated with the solvent and the mixture is then allowed to settle at a temperature below that at which the oil and the solvent are completely miscible. A separation into two layers takes place, the one, the so-called raflinate layer, consisting mostly of oil together with some dissolved solvent, and the other consisting mostly of solvent together with constituents extracted from the oil. The second layer is separated from the first layer and the solvent is removed from. the extract by means of distillation or by chemical means, the extract so obtained being used as raw material in my process. The extracts obtained by the treatment of kerosene stocks and Diesel oil stocks with liquid sulfur dioxide are specially adapted for use as raw materials in my process, although the extracts obtained with other selective solvents or the extracts obtained from lubricating oils may also be used and several advantages of my process will be retained.

According to' the present invention, the raw material, such as an extract from kerosene stock, is first submitted to cracking either in the liquid or in the vapor phase. Due to the highly unsaturated character of this stock, I prefer to carry out the cracking process at medium temperatures, such as, between 850 and 950 Fpbut lower or higher temperatures may also be used. It is also preferable to carry out the cracking under higher than atmospheric pressure, say under pressure of 100 to 1000 pounds per square inch in a tube and tank unit. The heavier distillate obtained in the cracking may be recycled for further cracking or the cracking may be carried out in a once through operation. The cracked material is separated into various useful products, such as naphtha, gas and a heavy residual product, the so-called cracked tar. The cracked tar is composed of thefollowing constituents:

l. Oily constituents soluble in naphtha and possessing the desirable quality of imparting green fluorescence to lubricating oils.

2. Asphaltic resins soluble in naphtha but adsorbed by fullers earth or other clays.

3. Asphaltenes insoluble in naphtha but soluble in benzene, chloroform and carbon tetrachloride. 4. Carbenes soluble only in carbon bisulfide.

5. Carboids insoluble in all solvents.

6. Asphaltic acids and anhydrides present-only in traces.

The preparation of a fluorescent dye or coloring body from the special cracked tar used as raw material consists then in the separation of the oily constituents and asphaltic resins by solvent action, followed preferably by the removal of resins by clay adsorption. The solvent used in the removal of the oily constituents and asphaltic resins from the other constituents of the tar is preferably an 86 A. P. I. gravity petroleum naphtha which has a very low solubility for asphaltenes and the other tar constituents. However, a heavier product, such as, for example, a 50 A. P. I. close out petroleum naphtha, may also be used with good results. The amount of naphtha used in the extraction of tar may be 100 to 600% by volume of the tar, but good results may be obtained with other percentages. Heating the tar and the naphtha to a moderate temperature, say 200 F., facilitates the mixing, but it is not mandatory. After cooling to about room temperature, the undissolved portion is separated from the solution by settling, filtration or by any other means. The naphtha is then stripped with fire and steam from the solution, the reduced heavy oily portion being ready for addition to lubricating oils to improve their cast.

The cracked tar may originally contain some gas oil and light lubricating oil fractions. These constituents have no desirable dyeing properties and should, therefore, be removed by distillation, either after the extraction with naphtha and removal of the naphtha or, preferably, before the tar is submitted to the treatment with naphtha.

The reduced heavy oil obtained after the removal of the naphtha may be used directly as a lubricating oil dye or it may be submitted to the usual refining process of acid and alkali treating, or to a process of acid treating, followed by clay treating or simply to a clay treating process. It is desirable to add the solvent, such as naphtha or a light lubricating oil to the reduced heavy oily product to insure fluidity at the treating temperature.

The reduced heavy oily product, preferably after clay treating, is added to a lubricating oil in quantities of say from 1 to 10%, although other proportions may also be used. The improved lubricating oil thus obtained may then be submitted to a finishing treatment with acid followed by clay treating.

Referring now tothe drawing, the sole figure separator t, in which the cycle stock and naphtha are separated from the tar. The former are taken overhead through line 5' and fractionated in an appropriate equipment (not shown). The tar is passed from the separator into the fluxing drum 6 in which a large quantity of naphtha is added thereto and the mixture is allowed to settle. The naphtha insoluble products are removed through the bottom line i while the soluble oil is passed into the stripping still 8 which is heated by any convenient method. Naphtha is taken overhead through .line 9 and reused while the naphtha soluble tar dye is further treated with acid and/or clay in treater l and then admixed to lubricating oil in mixing tank H. The lubricating oil containing the added heavy oily product may then be further treated in treater The following example will illustrate my process:

A heavy tar having a specific gravity higher than 1 and obtained by cracking a liquid S02 extract from a kerosene stock in a tube and tank unit at a temperature of 925 F. and under a pressure of 750 pounds per square inch is reduced under vacuum at a temperature of 650 F. to a 50% bottoms. The reduced tar is fluxed at 200 F. with an equal volume of a petroleum naphtha boiling between 280 and 380 F. After cooling and settling of the precipitated material, the naphtha is stripped from the solution using fire and steam. Twotreats are made with this reduced heavy oil in conjunction with a Coastal distillate of, approximately, 930 Saybold viscosity at 100 F. In the first treat 1% of this dye'is added and in the second treat 3%. The lubricating oil is then treated with 8 pounds of acid per barrel of oil, followed by contacting with 0.2 pound of clay per gallon of oil at 300 F. for one hour.

The inspection data of the untreated and treated lubricating oils are the following;

Percent dye stock 0 1 3 Pounds of acid per barrel 3 3, Pounds of clay per barrel 0. 2 0. 2 Color Robinson Dark 7% 1% Color Robinson after 16 hours at 250 F Dark 3% Oonradson carbon percent... 0. 0. 17 0.37 Ga Blue Olive green Olive green In another experiment 1% of the straight tar is added to the lubricating oil stock without prior treatment with naphtha. The oil thus obtained adapted to impart green fluorescence to lubricating oils when added thereto in small quantities,

which comprises subjecting an extract obtained by treating kerosene with liquid sulfur dioxide to cracking conditions suitable for the conversion thereof into lighter hydrocarbons and a tar, ex-

. tracting the tar so produced with from 100.-600% by volume of naphtha and removing the naphtha from the extract by distillation, leaving a heavy oily product having fluorescent properties.

2. A process of preparing a heavy oily product adapted to impart green fluorescence to lubricating oils when added thereto in small quantities, whichcomprises subjecting an extract of unsaturated character obtained by the selective solvent treatment of a petroleum oil with a solvent havfining of petroleum fractions to substantial cracking at high temperature and under superatmospheric pressure to form a pitchy residue which contains oil-soluble constituents having the desired coloring characteristics, and separating said constituents from the pitch by extraction with a solvent.

4. The method of preparing a material adapted to impart thereto a desired green fluorescence to lubricating oil which comprises subjecting extraction products separated in. the solvent refining of pertoleum fractions to substantial cracking at high temperature and under superatmospheric pressure to form a high melting point pitch which contains oil-soluble constituents having the desired coloring characteristics, mixing a mineral oil fraction with said pitch adapted to e-xtract said constituents therefrom, heating the resultingmixture to effect extraction, and removing the solvent liquid therefrom to produce the desired material in concentrated form.

5. The method of preparing a material adapted to impart a desired green fluorescence to mineral lubricating oil which comprises subjecting a liquid S02 extract of a kerosene stock to cracking at a temperature of about 925 F. under'a pressure of about 750 lbs/sq. in., reducing the resultant mixture to a 50% bottoms at a temperature of about 650 F. under vacuum, treating the resultant reduced tar under reflux conditions at about 200 F. with an equal volume of a petroleum naphtha having a'boiling point between about 280 F. and about 380 F., cooling, settling, separating the mixture, and stripping the solvent from the naphtha soluble portion of the tar to produce said material.

6. A process as in claim 5 wherein the resultant material is further subjected to acid treatment followed by clay treatment at an elevated temperature.

'7. A process as in claim 5 wherein the resultant material is mixed with a lubricating oil and said mixture treated'with acid at the rate of about 8 lbs. of acid per barrel of oil followed by contacting with finely divided clay at the rate of about 0.2 lb. of clay per gallon of oil at about 300 F. for at least one hour.

OLIVER H. DAWSON. 

